Illuminated panel and method for making same



Nov. 15, 1966 J. J. KAUP 3,284,941

ILLUMINATED PANEL AND METHOD FOR MAKING SAME Filed Sept. 19, 1963 WW I%9 'IIIIIIIIIII'III.

United States Patent Ofitice 3,284,941 Patented Nov. 15, 1966 3,284,941ILLUMINATED PANEL AND METHOD FOR MAKING SAME John J. Kaup, Chicago,Ill., assignor to Felsenthal Instruments, Inc., Chicago, 111., acorporation of Illinois Filed Sept. 19, 1963, Ser. No. 309,977 4 Claims.(Cl. 40-130) The present invention relates to a method for thepreparation of an illuminated panel, and to the manufactured panelitself. Panels of this character find particular utility in airborneswitch and communications equipment, but may also be utilized in variousdata processing control panels, and other control panels in whichdetailed lighted indicia are presented for viewing in darkened orcompletely darkened rooms.

Heretofore, various panels have been prepared in which luminescentlighting is employed. Luminescent lights of differing sizes areavailable which are formed by crystalline powders which are sandwichedbetween two electrically insulated surfaces, at least one of which istranslucent. Such lights, however, are in flat form, and can be veryexpensive both from the standpoint of illumination as well asmanufacture when cut into various sizes and shapes required for some ofthe complicated illuminated panel applications utilized in todaysaircraft. If such luminescent lamps are punched, or otherwise modifiedunder less than hermetical sealing and factory conditions, any moisturegetting into the crystalline powders employed will vastly reduce theefiiciency of the unit, and can greatly foreshorten its life if notdestroy the same upon contact.

Accordingly, it is one of the primary objects of the present inventionto provide an illuminated panel and method for making the same in whichall military standards are met for illumination; which is economical tomanufacture; durable in construction; and adaptable for a wide varietyof applications.

A related advantage of the present invention is to furnish anilluminated panel in which the illumination is achieved to the mostrigid specifications even though the panel is grey or black and whitefor daylight usage, the illumination being transmitted to the whiteportion, as a clearly defined red.

Still a further object of the invention looks to the uniform employmentof a green phosphorous lamp delivering a maximum of illumination, andafter an initial aging of 150 hours corrected to the aviation redstandard of .60 foot lamberts.

Still another advantage of the present invention is achieved byilluminating only the indica requred so that the current drain and totalpower consumption per panel is held to a minimum.

Another and very important object of the invention is to provide amethod for panel manufacture which permits the adaptability ofmanufacture readily to varying panel designs, the same being promptlyput into production on an economical basis.

A further and more detailed advantage of the invention looks to thepocketing of the light elements within the panel construction itself,thereby further insuring a hermetically sealed condition for the light.

Further objects and advantages of the present invention will becomeapparent in the following description of an illustrative embodiment inwhich:

FIG. 1 is a typical front elevation view of the type of panel in whichthe present illuminating features are achieved.

FIG. 2 is an exploded perspective view of an illustrative rear portionof the panel shown in FIG. 1 illustrating the sequential positioning ofthe electroluminescent lights and their wiring.

FIG. 3 is an enlarged transverse sectional view taken along 3-3 of FIG.1 through one of the lighting elements illustrating the various layersof sealant, luminescent paint and other details of the panel.

FIG. 4 is a partially diagrammatic exploded view of the same area asshown in FIG. 3 but illustrating an alternative embodiment thereof.

FIG. 5 is a further alternative embodiment of the construction of FIG. 3taken from the same position in diagrammatic exploded transversesection. In broad outline, the invention contemplates the employment ofa pair of plates, one of which is recessed in its rear portion toaccommodate the luminescent light panels of the invention, the lightpanels being embedded in the recessed areas after being appropriatelytreated to transmit the light to the specifications required; the rearplate portion being used to fully enclose and hermetically seal theentire panel in illuminated condition.

Referring now to the drawings, and more particularly FIG. 1 thereof, itwill be seen that a panel 10 of an illustrative character has aplurality of holes 11 throughout it which, for purposes of illustrationcould be used for switchboard plug-ins. porosity or perforations andapertures may exist in practice. It is within the scope of the inventionto provide a method for determining the design of each individual panel,and then fabricating and assembling the same in accordance therewith.There will first be described the method employed and in conjunctionwith this method, the various elements of the exemplary panel willbecome apparent.

Upon determining the particular intelligence to be transmitted by thepanel, the designer then orients the various illuminated indicia in alinear, or curvilinear form, the same being isolated into eitherelongate paths, or into clusters of rectangular or square nature. Everyattempt is made to eliminate circular openings which are enclosed byarcuately oriented indicia, but if the same is required, it is thenconcentrated into an area which can be defined by a rectangle of a givendimension.

After concluding the lamp layout, a clear acrylic plastic front plate12, as in one commercial embodiment approximately .l25 inch thick, issawed to an oversized rectangular size, or other configuration required.The material found highly adaptable in commercial usage is sold underthe trademark Plexiglas. The back plate 14 is similarly sawed to anoversized configuration, and is normally in such commercial embodimentsapproximately .060 inch thick.

The front plate 12 is then silk-screened with the copy on its face. Thepurpose of silk-screening the front plate first is to hold the cost ofthe particular elements to a minimum prior to the insertion of the lampsin the event that spoilage or rejects are encountered in the course oftesting with the lamps in place. Furthermore, after the lamps have beeninserted in the unit and tested satisfactorily, the risk of damage inthe course of silk-screening is substantial.

A white silk screen coating of approximately one mil in thickness isfirst applied. Any epoxy base paint is employed in silk-screening theWhite in place. With this thickness, the covering paint is translucent,and screens out only approximately thirty to forty percent of thetransmitted lighting behind it'.

A black reverse screen coating over the white is then employed, theblack thereby leaving showing the white beneath in the identicalconfiguration of the indicia 15 to be illuminated. The black reversescreen coating em- Vaiious other reasons for the ployed over the whiteone mil epoxy base paint is applied to a thickness of approximately oneto two mils.

Thereafter, depending upon the color of the host portion of the panel, areverse screen from the black screen coating is applied. The colorsgrey, blue, or black are commonly employed, but not necessarily to theexclusion of other colors. The base color is normally designed toprovide a daylight differential in illumination between the printedindicia 15 and the host portion, and yet sufficiently opaque to coverthe entire panel. One of the advantages of first applying the blackreverse screen coating, and then the ultimate color is to hold to theirreducible minimum the possibility of any coincidental pin holesthrough which undesired illumination might appear.

Thereafter, at least two locating holes 16 are drilled through the frontand back plates 12, 14 positioned so that they can subsequently beemployed as mounting holes. These holes are drilled undersizle, and.to adimension that is desirable for use in holding the front and rear platesin position for subsequent machining and assembly steps.

While the front plate is then held in position, a profile is preparedfor the routing of the mounting channels 18 of the lamps as well as themounting of the wiring in parallel. The layout of the mounting channels18 are shown in dotted lines in FIG. 1. The routing is done to a depthof approximately .060 inch inch) and finished to as smooth a channelbase surface 19 as conveniently compatible with accepted manufacturingtechniques.

The lamps 20 are silk-screened on the illuminated surface with aphosphorous red coating 21 to approximately .002 inch in thickness.Phosphorous red paints of this character are commercially available, oneexample is known as Velvaglow red manufactured by the Radiant ColorCompany of Oakland, California. Another is the Dayglow paintmanufacture-d by the Switzer Company of Ohio. The silk-screening to thetwo mil thickness is preferably done in two steps in order to controlthe quality and red translucent characteristics of the treated lamp.

Thereafter the various lamps are positioned in the mounting channels 18,and clamped on their rear portion in order to provide intimate contactbetween the phosphorous red coated surface 21 and the channel basesurface 19, and while clamped in this position are potted or otherwisesecured in place by the application of an epoxy potting resin 22 to theback portion 24 of the illuminating lamp. As was indicated above, thedepth of the routed out area is such that there is room for placing theepoxy over the rear which extends over the sidewalls of the illuminatinglamp and contacts the vertical side walls of the routed area and formsan intimate side wall chemical contact 25 therewith, at the same timesealing the lamps into position. The electrical lamp leads extendoutwardly from the lamp 20, and are positioned so that they may besoldered with circuit wires 28 which are subsequently placed intoposition. Because of the dielectrical characteristics of the epoxymaterial used to pot the lamp in position, a bare copper tinned wire of.025 inches can be employed as a circuit wire 28. The circuit Wires 28are then soldered into electrical connections with the leads 26extending from the lamp. The circuit wires 28 are laid atop the firstepoxy coating 22 in physical and electrical parallel relationship alongthe channels.

A second epoxy coating 29 is then placed into position to approximatelylevel off the routed area with the adjacent surface portion of the frontplate 12. While the second epoxy coating 29 is still in the softcondition, an ethylene dichloride solvent 30 is employed to theinterfaces of the back plate and the front plate, and thereafter theback plate is subjected to pressure in order to permanently bond it tothe front plate, and completely seal the instrument lamps 20 intoposition. Thereafter the instrument holes are machined out, and thefinal assemtrical connection for the ultimate illumination does notnecessarily form a critical element of the invention, it has beendetermined that a bayonet type fastener 31 which extends through theback plate and is soldered or otherwise secured to the two parallel leadlines between the back and front plate is highly advantageouscommercially.

Two alternative procedures are contemplated from the ones outlined aboveregarding the placing of the aircraft fluorescent red on the outerportion of the lamps. In the first variation (illustrated in FIG. 4) itis contemplated that the same thickness of red paint 21 be placed upon athin sheet of vinyl type plastic material 32 approximating 2 to 10 milsin thickness, and thereafter, the sheet material positioned in the baseportion of the routed out recesses in front of the lamps. In accordancewith the second alternative method contemplated (illustrated in FIG. 5)the base of the routed out portions are smoothed with a suitablesolvent, or molded smooth, or employed with a 3 plate construction, andthereafter painted directly with the red phosphorous type paint. Ineither application, the red paint, or other color to be transmitted, isplaced between the electroluminescent light and the top plate or outertop plate 34. The top plate is finished in accordance with the methodalreadydescribed in detail.

A further alternative is illustrated in FIG. 5 wherein an outer frontplate 34 has the indicia coating, and the lamp plate 35 has lampopenings 36 sawed or otherwise cut through its faces. The back plate 14remains the same. In assembly, the outer front plate is bonded to thelamp plate 35 in the same manner as the back plate attachment has beendescribed.

Although particular embodiments of the invention have been shown anddescribed in full here, there is no intention to thereby limit theinvention to the details of such embodiments. On the contrary, theintention is to cover all modifications, alternative embodiments, usagesand equivalents to the illuminated panel and method for making same asfall within the spirit and scope of the invention, specification andappended claims.

I claim:

1. An illuminated instrument panel comprising, in combination, a plasticlight transmitting front plate, translucent indicia on the outer face ofthe front plate for back lighting, means defining a plurality ofrecesses in the rear of the front plate and behind the translucentindicia, a plurality of electroluminescent lamps proportioned to nestwithin the recesses, electrical leads etxending from the lamps, acoating of red phosphorous between said lamps and the translucentindicia, a pair of circuit wires in electrically parallel relationshipatop a lamp and within the recess and connected to the lamp leads, alayer of potting resin embedding the circuit wires and lamps, and a backplate interfacially secured to and coextensive with the front plate,thereby sealingly embedding the electroluminescent lamps forbacklighting the instrument panel indicia.

2. An illuminated instrument panel comprising, in combination, a plasticlight transmitting front plate, a thin white coating on the front plate,an opaque reverse screen coating over the white defining colorcontrasting indicia for back lighting, means defining a plurality ofrecesses in the rear of the front plate and behind contrasting indicia,a plurality of electroluminescent lamps proportioned to nest within therecesses, electrical leads extending from the lamps, a coating of redphosphorous on said lamps and facing the indicia, circuit wires inelectrically parallel relationship atop the lamp and connected to thelamp leads, a layer of potting resin embedding the circuit wires andlamps, and a back plate interfacially secured to and coextensivewith'the front plate, thereby sealingly embedding .theelectroluminescent lamps for backlighting the instrument panel indicia.

3. An illuminated instrument panel comprising, in combination, a plasticlight transmitting front plate, a thin light colored translucent coatingon the front plate, an

opaque coating over the translucent coating leaving color contrastingindicia for back lighting, means defining a plurality of recesses in therear of the front plate and behind contrasting indicia, a plurality ofimperforate electroluminescent lamps proportioned to nest within therecesses, and having electrical leads extending therefrom, a coating ofred phosphorous between said lamps and the indicia, a first layer ofpotting resin covering the lamp in the recess from which the lamp leadsextend, a pair of circuit wires in electrically parallel and physicallyparallel relationship atop the first layer of potting resin meansconnecting the lamp leads to the circuit wires, a second layer ofpotting resin embedding the circuit wires, and a back plateinterfacially secured to and coextensive with the front plate, therebysealingly embedding the electroluminescent lamps for backlighting theinstrument panel indicia.

4. An illuminated instrument panel comprising, in combination, a plasticlight transmitting front plate, translucent indicia on the front platefor back lighting, means defining a plurality of elongate recesses inthe rear of the front plate and behind translucent indicia, a pluralityof elongate electroluminescent lamps proportioned to nest within therecesses, electrical leads extending from said lamps, a coating of redphosphorous between said lamps and the indicia, circuit wires inelectrical connection with the lamp leads, potting resin embedding thecircuit wires and lamps in the recesses, and a back plate interfaciallysecured to and coextensive with the front plate, thereby sealinglyembedding the electroluminescent lamps for backlighting the instrumentpanel indicia.

References Cited by the Examiner UNITED STATES PATENTS 2,444,026 6/ 1948Bartelheim 29- -155 .5 2,508,018 5/1950 Ellwood 29--l55.5 2,791,0505/1957 Neugass -130 2,919,366 12/1959 Mash 40-130 X 2,922,912 1/1960Miller 40130 X 3,038,271 6/1962 MacHutchin 40130 3,069,509 12/ 1962Sherron 313108 FOREIGN PATENTS 1,116,612 2/1956 France.

EUGENE R. CAPOZIO, Primary Examiner.

LAWRENCE CHARLES, Examiner. H. F. ROSS, Assistant Examiner.

4. AN ILLUMINATED INSTRUMENT PANEL COMPRISING, IN COMBINATION, A PLASTICLIGHT TRANSMITTING FRONT PLATE, TRANSLUCENT INDICIA ON THE FRONT PLATEFOR BACK LIGHTING, MEANS DEFINING A PLURALITY OF ELONGATE RECESSES INTHE REAR OF THE FRONT PLATE AND BEHIND TRANSLUCENT INDICIA, A PLURALITYOF ELONGATE ELECTROLUMINESCENT LAMPS PROPORTIONED TO NEST WITHIN THERECESSES, ELECTRICAL LEADS EXTENDING FROM SAID LAMPS, A COATING OF REDPHOSPHOROUS BETWEEN SAID LAMPS AND THE INDICIA, CIRCUIT WIRES INELECTRICAL CONNECTION WITH THE LAMP LEADS, POTTING RESIN EMBEDDING THECIRCUIT WIRES AND LAMPS IN THE RECESSES, AND A BACK PLATE INTERFACIALLYSECURED TO AND COEXTENSIVE WITH THE FRONT PLATE, THEREBY SEALINGLYEMBEDDING THE ELECTROLUMINESCENT LAMPS FOR BACKLIGHTING THE INSTRUMENTPANEL INDICIA.